Abstract : There exist several methods of interpreting magnetic anomalies, gravity anomalies and electrical anomalies which make use of the position of an inflexion point, this being one of the 'firmest' points in anomaly graphs. The application of these methods is somewhat restricted by the difficulty of locating inflexion points. Below we are setting forth a method is given of determining them and a simple instrument is described for carrying out the operation most speedily. (Author)